Magnetic tape is commonly used to store voice and data information due to its reliability, cost efficiency, and ease of use. Magnetic tape may be made more useful and cost effective by increasing the aerial density of information stored on the magnetic tape. This has generally been accomplished by including more data tracks on a given width of tape. While allowing more data to be stored, this increase in the number of data tracks requires a narrowing of the width of the data tracks, a narrowing of spacing between the data tracks, or both. As the data tracks are more closely spaced, positioning of the tape with respect to the tape head becomes more critical to reduce the possibility of errors introduced by reading or writing.
Tape heads generally include read elements for reading data from the magnetic tape and write elements for writing data to the magnetic tape. Typically, read elements may be formed in a read module with one read element for each data track that is to be read simultaneously. Similarly, write elements are manufactured into a write module, with one write element for each data track to be written simultaneously. To permit read-after-write operation on tape moving in either tape direction over the tape head, a typical tape head may include a sandwich of one write module between two read modules.
As the areal information density on magnetic tapes increases, the importance of accurately positioning the tape head relative to the magnetic tape also increases. One measure of the relationship between the tape head and the magnetic tape is the azimuth angle. The azimuth angle may be defined as the amount of rotation of the tape head about an axis through the tape and normal to the tape surface. An azimuth angle of zero implies that the tape head is rotationally aligned with the magnetic tape. Several problems may occur if the azimuth angle is too great. First, there may a loss of read amplitude if the read module is not aligned with data recorded on the magnetic tape. Second, in the case of a multiple element head, data buffer space may overflow due to the time skew between elements. Third, in the case of read-write-read heads implementing read-after-write operations, read elements must track corresponding write elements in order to check for write errors. Fourth, skew between the tape head and the magnetic tape creates relative vertical displacement between a read head in one read module and the corresponding read head in another read module. In order to minimize these effects, and because any tape written on one drive must be capable of being read on another drive, all tape heads must be aligned to a common azimuth standard.
Azimuth adjustment may be further complicated in tape drives that dynamically control the position of the tape head across the width of the magnetic tape. The tape head may be mounted in a carriage which is driven by an actuator to move the tape head across the tape width. Typically, the carriage and actuator are also rotated during azimuth adjustment.
Previous mechanisms permitting azimuth adjustment mount the tape head to one end of an arm with the opposing end fixed. The azimuth is adjusted by bending all or some of the arm about the fixed end. This caused translation of the tape head as well as rotation. Such translation cannot be absorbed within the closee tolerances required in a drive accessing high information density magnetic tape. Further, mechanisms employing an arm may not provide sufficient rigidity to support the carriage and the actuator.
What is needed is an azimuth adjustment mechanism that rotates the tape head about an axis through the center of the tape path. The mechanism should provide sufficient rigidity to support additional components such as the carriage and the actuator while still providing a sufficient range for azimuth adjustment.